Self-powered liquid oxygen pump and vaporizer



June 19, 1956 R. w. ARMSTRONG SELF-POWERED LIQUID OXYGEN PUMP AND VAPORIZER Filed Sept. 14, 1955 INVENTOR RIG/MRO W ARMSTRONG ATTORNEYS mm m mm mv mm m mm mm A A f i w Q Q S V. 174 MK mm mm m on A v G o E R vw H W 1 mm wk 1 mm mm wzazw 18 5558. I; 8 @255; 4

nited States Patent SELF-POWERED LIQUID OXYGEN PUMP AND VAPORIZER Richard W. Armstrong, Rockville, Md., assignor to the United States of America as represented by the Secretary of the Navy Application September 14, 1955, Serial No. 534,416

8 Claims. (Cl. 62-1) (Granted under Title 35, U. S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to self-powered automatic mechanisrns for converting a low pressure liquid to a high pressure gas in order, for example, to fill storage cylinders by a continuous process.

Heretofore, in the conversion of a liquid, such as liquid oxygen, to a pressurized gas of about 2,000 pounds per square inch (p. s. i.), it has been found necessary to use about 20 percent of the liquid for producing the gas necessary for processing the balance of the liquid. To avoid loss of this driving gas, theoretically it should be possible to condense the gas and return it to the liquid supply at low pressure. However, no practical condenser has been evolved, chiefly since the only condensing medium is the liquid oxygen or other substance, being pumped.

Generally stated the invention of this disclosure is an automatic liquid-gas conversion system in which the use of a condenser is made unnecessary for obtaining pressurized gas.

The objects of the invention are to provide apparatus for conversion of low pressure liquid to high pressure gas which is self-containing and automatic; to provide apparatus of the type described wherein use of a condenser is unnecessary; and to provide apparatus for conversion of liquid to gas which possesses mechanical simplicity.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein: the engine and pump units are disclosed together with the various valves, connections and other elements forming the converting system.

As illustrated, the system includes an engine A and pump B, these units being juxtaposed, end to end, with a common rod or shaft 10 thereinbetween. The engine comprises a casing 11 forming a cylinder for reciprocation of engine piston 12, this piston being provided on its top surface with a cut-away axial recess 13 with vertical end stops 14 and 15 for engine valve coaction as will be described hereinafter.

The top of the casing 11 is provided with a closure forming a housing 16 for a valve slide 17. This valve housing may be of any desired cross-sectional shape and may extend the full length of the engine cylinder. Valve ports are provided on the underside of this housing, two ports 18 and 19 at the left end of the cylinder, as shown in the figure, and two ports 20 and 21 at the right cylinder end. Also, a slot 22 is formed centrally of the valve housing on the underside thereof. On the upper side of the housing opposite lower housing ports 19 and 20 are high gas pressure inlets 25 and 26, respectively; also latch 27, including ball 28, screw 29 and intervening coil spring 30, is inserted in a tubular opening offset from the valve ice housing and placed between part 26 and a central outlet fitting 31 including the screw threaded nipple 32 and reducing coupling 33.

The valve slide 17 conforms in shape to the housing 16 and is provided with two port openings 35 and 36, one at either end of the slide, the length of the slide being such that when port 36 is in line with port 20 and inlet 26, and slide structure covers port 21, port 35 is positioned to the side of port 19 and inlet 25, with slide structure closing port 19 and inlet 25 and opening port 18, as shown in the figure. At this slide position the latch ball 28 rests in a depression 38, formed on the upper face of the slide. whereby the slide is held yieldingly against axial movement. A second depression 39, for reception of latch ball 28, is formed adjacent depression 38, the distance between these depressions being equal to the distance of slide port 35 from inlet 25 and the distances that the slide must move to close port 18 and open port 21.

Depending from the lower side of the mid area of valve slide 17' through housing slot 22 is a projection 40 having flat sides facing the ends of the valve. This projection has affixed thereto on both sides coil springs 41 and 42, the free ends of these springs being adapted for engagement with. piston steps 14 and 15, respectively, on movement of the piston to opposite limits in the cylinder.

The pump B comprises a heat insulated casing 45 which encloses the pump piston 46 slidably movable in cylinder 47, the cylinder being supported in the casing to permit free flow of liquid about the same. The piston 46 is attached to the pump end of the common shaft 10 between the engine piston 12 and pump piston and, to permit reciprocation of these combined pistons, a bearing 50, provided with clearance recesses 51 and pressure ports 52, if desired, for preventing high pressure oxygen from blowing into container 45, extends from engine casing 11 to a point within pump casing 45. The hearing at the pump end inside the casing is radially extended to form one end closure for the pump cylinder 47, there being provided ports 53 and 54 therein. Similarly, the opposite end of the pump cylinder is closed by a head plate 55 having ports 56 and 57 therein.

Casing 45, at the right end thereof as shown in the figure, is extended upwardly in an off-set heat insulated chamber for inclusion of a differential valve unit C. This unit includes a one-stepped piston 60 having a larger piston section 61 at the upper end and a smaller piston section 62 at the lower end. Enclosing this piston is a casing 63 formed with dual chambers 64 and 65 dimensioned to fit snugly over the piston sections. A duct 66 keeps the lower side of piston section 61 at chamber pressures; also, a curved recess about piston section 62, joined with a radial bore through the housing, forms an outlet port 67 for liquid. In accordance with the structure described it will be apparent from the figure, that the differential valve comprising piston 6162 has a fixed relationship to that of the driving piston 12 and the pumping piston 46. Accordingly, the pressures existing in the chambers 93 and are reflected as the pressures against the upper and lower surfaces respectively of the piston 61-62. As Will subsequently be made clear as the description pro ceeds, it is necessary that the pump discharge pressure from chamber 85 be slightly greater than the equilibrium pressure corresponding to the chosen pump, engine and differential valve areas. However, as is apparent in the figure, the pressure on the face of the differential valve piston 61 is the same as that in chamber 93. Because of the friction manifested by the pumping piston 12, however, it is therefore necessary to provide an additional bias on the differential valve piston 6162. The spring 68 provides such degree of bias. Normally, chambers 64 and 65 and piston sections 61 and 62 are cylindrical.

The additional units of the converting system include the warming coil D for the receiver, the receiver E which may be one or more receptacles for the compressed gaseous product of the system and warming coil F for converting the pressurized liquid into engine operating gas. Both receiver warming coils and engine warming coils are normally subjected to room temperatures.

Having delineated the system units, the relationship between these units and the fluid connections and controls therein will now be described.

Connecting pump cylinder port 53 to the engine warming coil F is a pipe line 70 in which is positioned a oneway valve 41 permitting outflow only from the pump chamber. Pipe 72 with branch pipe 73 connects the engine warming coil to engine valve inlets 25 and 26. Engine valve outlets 13, 31 and 21 are connected by a common branch pipe system 74 directly to the receiver B through receiver valve 75, the 31-74 branch serving as a leakage outlet from the engine cylinder. A leakage duct 76 also connects the bearing of shaft in the engine head. It is noted that pressures developing in pipe system 74 bear equally on the ends of valve slide 17 in the line of slide movement, thus reducing the force required to move the slide to a minimum.

Pipe 70 between the pump and warming coil F is provided with a branch pipe 77 located inside the pump casing and making a junction with pipe 78 leading from the pump outlet 56 through one-way valve 79, pipe 78 connecting the pump B to the chamber 65 of differential valve C. The warming coil D is provided with a pipe line 89 to the differential valve outlet port 67 for reception of pump liquid and pipe lines 80 and 81 for supply of gas to the receiver through valve 75 and for supply of gas to differential valve chamber 64. The pump B is equipped, also, with one-way valves 82 and 83 permitting entry, only, of liquid into pump chamber sections 85 and 86, respectively, through ports 54 and 57.

In the operation of the converting unit, it may be assumed that the pump chamber 45 is filled with liquid oxygen to the level indicated at 90, at a pressure of one atmosphere. Assume, also, that the engine is moving the piston 46 to the left, pressurizing the liquid in chamber section 85, and hence moving the liquid through port 53 and pipe line 70 to Warming coil F and drawing liquid into pump chamber 86 through one-way valve 83. At F, gas forms with pressures higher than that of the receiver, which is transmitted through pipes 72, 73 and valve port 36 to engine cylinder section 92, thus forcing the engine piston to the left.

At the same time, liquid oxygen moves through branch pipe 77 in the pump casing to differential valve chamber 65. Differential valve 60 is under gas pressure from the receiver of approximately one-half of the pump pressure to hold the valve closed, but as the pump pressure increases a point is reached where the ratio of pump to receiver pressure exceeds the ratio of the areas of the differential valve piston sections 61 and 62 and port 67 opens feeding liquid oxygen to the warming coil D. Gas, forming in the warming coils develops pressure in differential valve chamber 64 through pipe 81 to a point where port 67 closes. The tension of spring 68 is set so that there is always a minimum pressure sufficient to overcome the friction of the pump mechanism when the pressures are balanced. Excess gas from the warming coil D enters the receiver E through branch pipe section 80.

When the engine piston in its movement to the left contacts coil spring 42, a spring pressure is reached sufiicient'to move the valve slide to the left, the latch ball 28 moving out of depression 38 and seating in depression 39. At this new slide position valve port 18 is closed stopping used gas flow from the engine to the receiver at this point, and port 19 is opened to receive gas under pressure from the engine warming coils F. Also, port 20 to the warming coils F is closed and port 21 to the receiver opened. Thus, pressure is now developed in engine cylinder 93, moving the engine piston 12 to the right and repeating the described cycle, forcing pump liquid from pump chamber 86 through outlet 56, oneway valve 79 and pipe 78 tothe differential valve C, and drawing fresh liquid into pump chamber through oneway valve 82. Thus pump action proceeds until the force created by the receiver pressure, applied to the differential piston of the valve C, exceeds that of the force due to the pump pressure, thus maintaining an automatic flow control.

It will now be evident that the apparatus as described permits automatic development of receiver pressure, Without the use of condenser mechanism. This is supported by the underlying theory which indicates at equilibrium conditions that VE(PEPR) VPPE (1) Where Vp volume of pump piston displacement; Va volumc of engine piston displacement; PE=pressure in engine warming coils and engine driving pressure; Pn=pressure in receiving container and its warming coils.

It VP be written as KVE, Equation 1 may be Written as PR=(1K)PE This may be written as APR=(1K)APE If PE max. and PR max. be tabulated as a function of K the following relationships appear.

K APE/APE PE max. P max.

p. s. t. p. s. i. /4 2,500 1, 875 ,6 l6! 5,000 2, 500 $4 7, 600 1, 876

The above table indicates that in practice a receiver gas pressure of 2000 p. s. i. should be readily attainable.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. Apparatus for converting low pressure liquid to high pressure gas, comprising an engine having gas inlet and outlet ports, a warming coil connected to said engine for supply of high pressure engine actuating gases thereto, a pump operated by said engine to supply liquid to said engine warming coil, a receiver for storage of gases under pressure, conduits between the engine exhaust outlets and said receiver, a warming coil for supplying gas to said receiver, and a differential valve connected between said receiver warming coil and said pump, said valve normally passing liquid from said pump to said receiver Warming coil only when the force due to the pump pressure exceeds that of the force due to the receiver pressure as developed at said differential valve.

2. The liquid-gas conversion apparatus as defined in claim 1, said differential valve comprising a housing having two series connected chambers of ditferent maximum diameters therein, the larger diameter chamber being permanently connected to the receiver, a stepped piston conforming to the diameters of said chambers mounted for slidable movement therein, and a port connecting said smaller chamber to the receiver, said port being closed when the force on the larger piston section as obtained from said receiver pressure exceeds the opposing force applied on the smaller piston section from said pump pressure.

3. The liquid-gas conversion apparatus as defined in claim 1, said pump comprising a cylinder, inlet and outlet valves at each end of said cylinder, a piston slidable within said cylinder, a piston rod connecting said piston to said engine for reciprocation thereby, and a casing for enclosing said pump cylinder, said casing being spaced from said cylinder whereby the cylinder may be completely immersed in liquid in said casing.

4. The liquid-gas conversion apparatus as defined in claim 1, said dilferential valve comprising a housing having an outlet port in the wall thereof, and a free floating piston in said housing having pressure terminals positioned toward the pump and receiver respectively, said valve being adapted to open said outlet port for passage of pump liquid to the receiver only when the force due to said pump pressure on the pump terminal of the piston exceeds the force due to said receiver pressure on the receiver terminal.

5. The liquid-gas conversion apparatus as defined in claim 4, wherein the ratio of the area of the pressure terminal of the said differential valve piston exposed to engine driving pressure divided by the area of the pressure terminal exposed to receiver pressure is equal to 1-K, where K is equal to the ratio of the pump piston area divided by the engine piston area.

6. The liquid-gas conversion apparatus as defined in claim 1, said engine comprising a cylinder, a piston slidable in said cylinder, a piston rod attached to said piston and adapted for connection to said pump, said inlet and outlet ports being positioned at each end of said cylinder, a valve slide for opening and closing said ports on reciprocation of the slide, and actuating means between said piston and slide for reciprocating said slide on reciprocation of said piston.

7. The liquid-gas conversion apparatus as defined in claim 6, said piston having an axially alined recess on the side thereof adjacent said slide provided with transverse radial ends, and said actuating means including a finger depending from said slide about midway thereof into said cylinder recess and an axially alined spring attached at one end only to each side of said finger and adapted on piston movement to engage the recess ends in said piston.

8. The liquid-gas conversion apparatus as defined in claim 7, and means for yieldingly holding said slide at either limit of reciprocation.

References Cited in the file of this patent FOREIGN PATENTS Great Britain June 30. 1932 

1. APPARATUS FOR CONVERTING LOW PRESSURE LIQUID TO HIGH PRESSURE GAS, COMPRISING AN ENGINE HAVING GAS INLET AND OUTLET PORTS, A WARMING COIL CONNECTED TO SAID ENGINE FOR SUPPLY OF HIGH PRESSURE ENGINE ACTUATING GASES THERETO, A PUMP OPERATED BY SAID ENGINE TO SUPPLY LIQUID TO SAID ENGINE WARMING COIL, A RECEIVER FOR STORAGE OF GASES UNDER PRESSURE, CONDUITS BETWEEN THE ENGINE EXHAUST OUTLETS AND 